Formation and desorption of aluminum hydride from hydrogen adsorbed aluminum surfaces

Hara, Masahiko; Domen, Kazunari; Onishi, Takaharu; Nozoye, Hisakazu; Nishihara, Chizuko; Kaise, Y.; Shindo, Hitoshi

doi:10.1016/0039-6028(91)90309-g

Cited by 54 publications

(36 citation statements)

References 9 publications

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“…The vacancies formed in real time during exposure to H2, which indicates that the exposure has a role in their formation. This is consistent with previous reports of atomic H absorption by Al [9][10][11][12][13] . The observed vacancy cluster formation is also evidence for the proposed role of Ti in the dissociation of H2 into atomic H, as no such vacancies were observed on the bare Al surface.…”

Section: Resultssupporting

confidence: 93%

“…Pure Al does not react with hydrogen to form alane at room temperature unless subjected to impractically high hydrogen pressures exceeding 7 kbar [1,8] . Early studies [9][10][11][12][13] have shown that atomic H can react with the Al(111) surface to form alane, as evidenced by products containing alane-derived species. A scanning tunneling microscopy (STM) study, supported with surface infrared measurements by Go et al [14][15] showed that the etching of Al(111) by atomic H occurs at both steps and terraces.…”

Section: Introductionmentioning

confidence: 99%

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Towards Direct Synthesis of Alane: A Predicted Defect‐Mediated Pathway Confirmed Experimentally

et al. 2016

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Alane (AlH3) is a unique energetic material that has not found a broad practical use for over 70 years because it is difficult to synthesize directly from its elements. Using density functional theory, we examine the defectmediated formation of alane monomers on Al(111) in a two-step process: (1) dissociative adsorption of H2 and (2) alane formation, which are both endothermic on a clean surface. Only with Ti dopant to facilitate H2 dissociation and vacancies to provide Al adatoms, both processes become exothermic. In agreement, in situ scanning tunneling microscopy showed that during H2 exposure, alane monomers and clusters form primarily in the vicinity of Al vacancies and Ti atoms. Moreover, ball milling of the Al samples with Ti (providing necessary defects) showed a 10 % conversion of Al into AlH3 or closely related species at 344 bar H2, indicating that the predicted pathway may lead to the direct synthesis of alane from elements at pressures much lower than the 104 bar expected from bulk thermodynamics. [d,f] S. Gupta, [a] and V. K. Pecharsky* [a,c] Abstract: Alane (AlH3) is a unique energetic material that has not found broad practical use for over 70 years due to difficulties of its direct synthesis from elements. Using density functional theory we examine the defect-mediated formation of alane monomers on Al(111) in a two-step process: (1) dissociative adsorption of H2 and (2) alane formation; both are endothermic on clean surface. Only with Ti-dopant to facilitate H2 dissociation and vacancy to provide Al adatoms, both processes become exothermic. In agreement, in situ scanning tunnelling microscopy showed that during H2 exposure alane monomers and clusters form primarily in the vicinity of Al vacancies and Ti atoms. Moreover, ball-milling samples of Al with Ti (providing necessary defects) showed a 10% conversion of Al into AlH3 or closely related species at 344 bar H2, indicating that the predicted pathway may lead to direct synthesis of alane from elements at pressures much lower than the 10 4 bar expected from bulk thermodynamics.

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Section: Resultssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Towards Direct Synthesis of Alane: A Predicted Defect‐Mediated Pathway Confirmed Experimentally

et al. 2016

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“…and the H-induced etching of aluminum to form hydride, as has been extensively observed in vacuum experiments [25][26][27][28][29][30] Al + 3H → AlH 3 ͓3͔…”

Section: ͓1͔mentioning

confidence: 72%

“…24 Although no reports of peaks for the secondary anions AlD − or D − were found in the literature, cations such as AlH + , AlH 2 + , and AlH 3 + have been detected upon exposing clean Al surfaces to hydrogen. [25][26][27][28][29][30] These cations have been shown to result from aluminum hydride species ͑AlH 3 ,Al 3 H 6 ͒ formed by the chemical reaction of Al with hydrogen. Based on these comparisons to the literature, the AlD − peak is not due to deuteroxyl groups in the surface film and is more likely attributable to an aluminum deuteride surface species.…”

Section: Discussionmentioning

confidence: 99%

Formation of Aluminum Hydride during Alkaline Dissolution of Aluminum

Adhikari

Lee

Hebert

2008

J. Electrochem. Soc.

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The role of hydrogen-containing surface species in the alkaline dissolution of aluminum was studied by secondary ion mass spectrometry ͑SIMS͒ and atomic force microscopy ͑AFM͒. The measurements revealed quasi-periodic nucleation and dissolution of large number densities of 10-100 nm size particles, during open-circuit dissolution in 1 M NaOH͑D͒ at room temperature. SIMS results using deuterated solutions, and prior Auger microprobe measurements, indicated that the particles were composed of aluminum hydride ͑deuteride͒, with an aluminum hydroxide ͑deuteroxide͒ surface layer. The measured open-circuit potential during dissolution was close to the Nernst potential of hydride oxidation. It was concluded that AlH 3 forms continuously during dissolution by reaction of cathodically generated hydrogen with the Al metal and is oxidized to aluminate ions ͓Al͑OH͒ 4 − ͔ in the accompanying anodic process. The present results are a direct confirmation of hydride formation on Al accompanying corrosion.

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“…[13][14][15][16][17][18] The hydride then oxidized according to the reaction identified by Perrault The present paper examines whether the electrochemical behavior of anodic Al dissolution in alkaline solutions supports the participation of AlH 3 as a reaction intermediate. Results of cyclic voltammetry ͑CV͒ and potential step experiments are interpreted using models for the Al electrode based on the proposed mechanism.…”

Section: Al + 3h → Alh 3 ͓2͔mentioning

confidence: 99%

Participation of Aluminum Hydride in the Anodic Dissolution of Aluminum in Alkaline Solutions

Adhikari

Hebert

2008

J. Electrochem. Soc.

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The mechanism of anodic alkaline dissolution of aluminum was investigated through the analysis of cyclic voltammetry (CV) and potential step experiments. Attention was focused on the role of aluminum hydride (AlH3) as a reaction intermediate, as suggested by the recent detection of AlH3 formation during open-circuit dissolution. Potential step experiments at pH 11.75 revealed that the potential at the metal–surface film interface was close to the Nernst potential of AlH3 oxidation. This finding suggested a reaction mechanism in which an interfacial AlH3 layer is formed continuously by reaction of cathodically formed H with Al, and is then oxidized to the dissolution product, aluminate [Al(OH)4−] ions. However, potential step experiments at pH 11 did not indicate the presence of interfacial AlH3 ; instead, the metal–film interface was close to the equilibrium potential of Al oxidation. Analysis of the CV indicated an abrupt transition in dissolution behavior between the two pH values, from a relatively rapid dissolution controlled by diffusion and film conduction in highly alkaline solutions, to a slow dissolution at a lower pH controlled by a highly resistive surface film. The formation of interfacial AlH3 occurs readily at the higher pH, but is suppressed as the pH approaches neutrality.

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Formation and desorption of aluminum hydride from hydrogen adsorbed aluminum surfaces

Cited by 54 publications

References 9 publications

Towards Direct Synthesis of Alane: A Predicted Defect‐Mediated Pathway Confirmed Experimentally

Towards Direct Synthesis of Alane: A Predicted Defect‐Mediated Pathway Confirmed Experimentally

Formation of Aluminum Hydride during Alkaline Dissolution of Aluminum

Participation of Aluminum Hydride in the Anodic Dissolution of Aluminum in Alkaline Solutions

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